It is well known that a structure may develop crack under cyclic loading. Sources of the cyclic loading can come from normal operation or vibrations during transportation. Once a crack is initially developed, the crack may propagate due to a number of possible factors, including but not limited to, continued operational loading, combined effect from environment and or temperature, etc. In certain extreme situations, the crack can propagate so much to cause structural failure. Therefore, it is vitally important to monitor the development and propagation of cracks in a structure to ensure that the structural integrity is maintained.
With advent of various engineering disciplines, there are several techniques that can assist a user (i.e., scientists, engineers, etc.) to perform this difficult determination. For example, Computer Aided Engineering (CAE) has been used for supporting engineers in many tasks, particularly CAE (e.g., finite element method, boundary element method, meshfree method, etc.) can be used for obtaining numerically simulated structural behaviors (e.g., crack propagations) in a time-marching simulation of structure under a cyclic loading.
FEA is a computerized method widely used in industry to simulate (i.e., model and solve) engineering problems relating to complex products or systems (e.g., cars, airplanes, etc.) such as three-dimensional linear and/or non-linear structural design and analysis. FEA derives its name from the manner in which the geometry of the object under consideration is specified. The geometry is defined by elements and nodes. There are many types of elements, for example, solid elements for volumes or continua, shell or plate elements for surfaces and beam or truss elements for one-dimensional structure objects.
However, it is generally difficult to physically determine or measure the length of a crack especially when the crack propagates inwards within a structure.